Surgical Oncology: Canine Oral Fibrosarcoma

A 10-year-old, female spayed Labrador retriever presented with a caudal maxillary and palatine mass. The owners noted a right-sided facial swelling with associated halitosis 3 weeks prior to presentation. The referring veterinarian initially suspected a tooth root abscess, but she did not respond to a 14 day course of amoxicillin-clavulanic acid. The dog was then referred for further evaluation and treatment.

Preoperative Evaluation

A complete blood count and serum biochemistry were performed on 6th February 2017 and the only abnormalities were mild increases in ALP (246 U/L, reference range 20-150 U/L) and total calcium (2.98 mmol/L, reference range 2.15-2.95 mmol/L). An ionized calcium blood test was performed and this was within the normal reference range (1.27 mmol/L, reference range 1.12-1.40 mmol/L). Three-view thoracic radiographs showed no evidence of pulmonary metastasis. An aspirate of the right mandibular lymph node was performed, but cytology was non-diagnostic.

An intraoral exam performed under sedation revealed a 5.0cm x 5.8cm mass involving the right caudal maxilla and hard palate (Figure 1). The mass had an intact mucosal covering.

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Figure 1. Preoperative appearance of a right maxillary and palatine mass, with the mass extending to the midline of the hard palate.

The first part of sentinel lymph node mapping procedure was performed 24hrs prior to CT scan with 1.2ml Lipidiol injected in four quadrants around the mass under sedation. The following day, a sedated pre-and post-contrast CT scan was performed of the head and neck, and post-contrast CT scan of the thorax. Following completion of her CT scan, an incisional biopsy of the mass was performed with an 8mm punch biopsy. Histopathology of the incisional biopsy was consistent with a high-grade oral fibrosarcoma.

The CT scan showed a right caudal maxillary mass with invasion into the right nasal cavity and extension of the mass across the midline of the hard palate (Figure 2). There was no evidence of nodal or pulmonary metastasis, and the ipsilateral (right) mandibular lymph node was identified as the sentinel lymph node. These findings were discussed with the owner as well as on the Veterinary Society of Surgical Oncology (VSSO) listserv, in particular reconstruction of the palatine defect following resection. After lengthy discussions, the owner elected to proceed with surgery.

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Figure 2. Preoperative CT scan showing a caudal maxillary mass invading into the nasal cavity and extending across the midline of the hard palate.

Surgery

The plan was to resect the oral fibrosarcoma via a combined (dorsolateral-intraoral) approach and reconstruct the palatine defect with a facial axial pattern flap. The facial axial pattern flap would be used a distant flap with the flap transposed through the lip and then released 4 weeks postoperatively.

The dog was anesthetized, positioned in left lateral recumbency, clipped, aseptically prepared, and draped for surgery. The pharynx was packed to prevent aspiration of blood and surgical fluids. A mouth gag was inserted to maintain the mouth in an open position. A skin incision was performed along the ventral border of the right zygomatic arch and extended caudally to the level of the wing of the atlas (for the facial axial pattern flap) and rostrally over the dorsolateral aspect of the right muzzle (for the combined approach for the hemimaxillectomy). A second skin incision was performed along the ventral border of the right mandible equidistant the dorsal incision and the caudal border of the facial axial pattern flap was then created with a skin incision joining the dorsal and ventral incisions. The facial axial pattern flap was undermined deep to the panniculus muscle and a bridging incision was created ventrally at the level of the caudal commissure of the lips (Figure 3). The mandibular and medial retropharyngeal lymph nodes were excised through this exposure and bleeding was controlled with cautery.

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Figure 3. The facial axial pattern flap being raised for reconstruction of the palatine defect following resection of the maxillary and palatine high-grade fibrosarcoma.

The gingival mucosa was incised from the right canine tooth to the second molar tooth with 2cm soft tissue margins around the 5.0cm x 5.8cm palatine and caudal maxillary fibrosarcoma. Blunt dissection and a periosteal elevator were used to connect the skin and intraoral mucosal incisions to create a bipedicle flap (Figure 4a). The palatine mucoperiosteum was incised 2cm around the maxillary and palatine mass. Osteotomies with 2cm bone margins were performed with a biradial saw rostral to the canine tooth, and with an oscillating saw laterally and rostrally along the maxillary bone, dorsally along the maxillary bone, ventrally along the palatine bone, and then finally caudally within the inferior orbit to connect the palatine, caudal maxillary, and dorsal maxillary osteotomies with retraction of the globe. Right-sided turbinectomy was performed because of intranasal extension of the fibrosarcoma. The bone segment was removed and the surgical site lavaged with sterile isotonic saline (Figure 4b).

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Figure 4a (left) with the high-grade fibrosarcoma being exposed after ventral reflection of the bipedicle labial flap. Figure 4b (right) showing the palatine defect following wide excision of the high-grade oral fibrosarcoma.

The facial axial pattern flap was rotated into the intraoral defect to reconstruct the palatine resection. Holes were predrilled into the palatine bone with a 2mm drill bit. The subcutaneous tissue of the facial axial pattern flap was sutured to the predrilled palatine holes with a 3-0 PDS simple interrupted suture pattern. The subcutaneous tissue of the facial axial pattern flap was sutured to the submucosa of the palatine mucoperiosteum with a 3-0 PDS simple continuous suture pattern. The skin of the facial axial pattern flap was sutured to the palatine mucoperiosteum with a 3-0 PDS simple continuous suture pattern (Figure 5). Laterally, the subcutaneous tissue of the facial axial pattern flap was sutured to the labial submucosa with a 3-0 PDS simple continuous suture pattern. The skin of the facial axial pattern flap was sutured to the labial mucosa with a 3-0 PDS simple continuous suture pattern. The remaining incisions were closed with 3-0 Monocryl simple continuous suture pattern (subcutaneous) and 3-0 Nylon cruciate pattern (skin).

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Figure 5. The facial axial pattern flap has been transposed into the oral cavity to reconstruct the palatine defect via a bridging incision at the caudal commissure of the lips. Note the size of the facial axial pattern flap relative to the palatine defect. Both the bridging incision and size of the flap relative to the defect would result in postoperative complications.

The oral mass was confirmed as a high-grade fibrosarcoma with a histologically complete excision and no histologic evidence of lymph node metastasis.

Postoperative Management

The dog did not have a smooth recovery with constant pawing at her mouth and inspiratory difficulties. These required sedation for management. The pawing at her mouth was suspected to be a result of the facial axial pattern flap within her mouth. The inspiratory difficulties were suspected to be caused by the paradoxical movement of the flap with respiration within her oral cavity. In retrospect, the flap was likely too large for the defect and should have been trimmed to provide a better fit into the palatine defect. On further consultation with other surgical oncologists on the VSSO listserv, the pawing at the mouth was a commonly encountered problem with transposition of haired skin flaps into the oral cavity of dogs. This typically resolves after 3 days, but unfortunately did not resolve in our patient.

An anesthetized exam on postoperative day 6 showed thickening of the flap with distal flap necrosis. There was no evidence of distal flap necrosis 2 days postoperatively. The sutures were removed and the flap was serially debrided until bleeding was noted from the debrided edges of the flap. In total, approximately 40% of the flap area was debrided. The facial axial pattern flap was also transposed into the oral cavity via a bridging incision at the caudal commissure of the lips. This was released and the caudal commissure of the lips was reconstructed. A full-thickness skin incision was made in the caudal aspect of the right upper lip. The base of the flap was tubed with two 3-0 Monocryl simple interrupted sutures and passed through the caudal aspect of the upper lip. There was sufficient length remaining in the flap to be able to reconstruct the palatine defect in combination with a labial mucosal-submucosal flap.

While recovery from this second surgery was not smooth either with repeated pawing at her mouth, this behaviour subsided after 3-4 days. Further treatment was required for management of oronasal fistulae due to areas of dehiscence at the flap-mucosal junction, but these involved local debridement and resuture without the need for further flaps. Supplemental nutrition was provided via an esophagostomy tube.

Six weeks after her initial surgery, the base of the facial axial pattern flap was released and sutured into location in the caudal oral cavity and the lip defect was sutured. The epidermal surface of the haired flap within her oral cavity was removed (Figure 6). Her esophagostomy tube was also removed at this time. Following this planned revision surgery, the dog returned to normal eating with no further complications.

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Figure 6. Appearance of the distant facial axial pattern flap following release and removal of the epidermal surface at the time of the initial release (left) and 1 week post-release.

Learning Points

One of the reasons I enjoy surgical oncology is that sometimes there are challenging cases for which you have to think out of the box. This was a large palatine defect which could not have been reconstructed with standard labial mucosal-submucosal flaps. The angularis oris axial pattern flap was considered, but I preferred the facial axial pattern flap (see Yates et al, Aust Vet J, 2007). The facial axial pattern flap has three direct cutaneous arteries (superior and inferior labial arteries and the angularis oris artery) and hence is a sturdy flap with a high success rate. While the flap was eventually successful, the flap was too large relative to the size of the palatine defect and this caused paradoxical movement of the flap with respiration which lead to inspiratory difficulties and likely partial flap failure. In future cases, the flap should be trimmed to match the size of the defect. I also transposed the facial axial pattern flap into the oral cavity via a bridging incision at the caudal commissure of the lips and this was very irritating for the dog, resulting in prolonged pawing at the mouth. She tolerated transposition of a tubed flap through the lip much better than this bridging incision, which is understandable in retrospect.

This was a difficult case for the owner as well as hospital staff. Complications are never desired, but are a reality of practice, and can result in decreased morale for the surgeon and support staff, especially when the complications are difficult to manage. The complications experienced in this patient were not particularly difficult to manage, but the complications were viewed as more worrisome than normal because of the location of the flap within the oral cavity. Complications with axial pattern flaps are very common and are reported in up to 89% of cats and dogs (see Field et al, J Small Anim Pract, 2015). The majority of these complications are minor and are managed with either surgical revision or conservatively. This was also true for this dog, but they seemed more severe because of the frequent pawing at the mouth and the frequent need for evaluation of the oral cavity under anesthesia because this not possible while conscious.

As a result of these complications and the stress it caused the hospital staff to observe a distressed dog pawing at her mouth, there were some calls for the dog to be euthanized. While I understand this emotion, there were a number of factors that were not being considered in making this call. The owner decided to pursue surgery, as well as management of the complications, following discussions at every time point and had given collaborative informed consent to proceed at each stage. The decision to euthanize or not is entirely dependent on the owner provided that the animal is being treated humanely. In this case, the complications were minor, despite being located in the oral cavity, and there were many potential benefits following successful resolution of these complications. The median survival time following surgery for oral fibrosarcoma is 743 days with overall 1- and 2-year survival rates of 88% and 58%, respectively (see Frazier et al, Vet Comp Oncol, 2012). These outcomes are very encouraging and hence the management of the postoperative complications were worthwhile considering that the owner now has her dog back (with normal appetite, eating behaviour, and activity levels) and that she will hopefully live out her days cancer-free.

Submitted by: Dr. Julius M. Liptak

BVSc, MVetClinStud, FACVSc, DACVS, DECVS, ACVS Founding Fellow in Surgical Oncology

VCA Canada-Alta Vista Animal Hospital, Ottawa, Ontario, Canada

[email protected]

References:

G Yates, B Landon, G Edwards, et al. Investigation and clinical application of a novel axial pattern flap for nasal and facial reconstruction in the dog. Australian veterinary journal 2007;85:113–118

http://onlinelibrary.wiley.com/doi/10.1111/j.1751-0813.2007.00111.x/full

EJ Field, G Kelly, D Pleuvry, et al. Indications, outcome and complications with axial pattern skin flaps in dogs and cats: 73 cases. JSAP 2015;56:698–706.

http://onlinelibrary.wiley.com/doi/10.1111/jsap.12400/full

SA Frazier, SM Johns, J Ortega, et al. Outcome in dogs with surgically resected oral fibrosarcoma (1997–2008); VCO 2012;10:33–43,

http://onlinelibrary.wiley.com/doi/10.1111/j.1476-5829.2011.00272.x/full

 

 

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